Pulse generator system



Jan. 27, `1948. D. D. GREG' 2,434,920

PULSE GENERATOR SYSTEM Filed Nov. 23, 1943 2 Sheets-Sheet 1 FREQUENCY 2 J2 v n M- W v Y INVENTOR. 7o/m20 a G/P/fa HMP( l TUDE Filled Nov. 25, 1943 PULSE GENERATOR SYSTEM 2 Sheets-Sheet 2 Patented Jan. 27, 1948 PULSE GENERATOR SYSTEM Donald D. Grieg, Forest Hills, N. Y., assgnor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application November 23, 1943, Serial No. 511,406

This invention relates to wave and pulse generating systems particularly useful in radio and other electrical circuits.

It is one of the objects of my invention to provide a system for producing, from any given pulse shape, a wave of substantially a given amplitude characteristic fo-r any desired frequency within a given wide band of frequencies and/or a pulse of any desired width within wide limits.

It is another object of my invention to provide a System for producing, from energy of a periodic wave or a train of recurring pulses, damped Waves of substantially a given amplitude characteristic for any desired frequency within a given wide band of frequencies and in which the frequency selected is independent of the frequency of the input wave, the input pulse width or the input pulse repetition rate; or for producing from any such input energy a train of pulses having any desired pulse width within given limits.

A further object of my invention is to provide a system for producing, from a pulse substantially rectangular in Shape, an edger pulse in which one edge (either the leading or trailing edge) is substantially vertical and the other is curved gradually in its build-up or decay as the case may be.

One of the important features of my invention comprises the generation of the edger pulse" which, according to my definition, is a pulse form having one edge, either leading or trailing, which is substantially vertical while the other opposite edge is curved gradually, preferably in an exponential manner, in its build-up or decay. This edger pulse may be generated according to my invention from a pulse or undulation of any shape or width.

The edger pulse is particularly useful to shock excite a resonant circuit in conjunction with a damper means for producing damped waves of substantially a given amplitude characteristic for any desired frequency within a given wide band of frequencies or for producing pulses of -any desired width within wide limits, the selection of frequency or pulse Width being accomplished by merely controlling the tuning of the resonant circuit. The frequency of the wave produced is independent of the frequency or pulse repetition rate of the input energy and most important is also independent of the pulse width of the undulations or pulse Shapes of the original input energy. Further, the widths of the pulse output of the system are independent of the widths of the input undulations or pulses.

The above and other objects and features of Claims. (Cl. 25o-27) the invention will become more clear upon consideration of the following detailed description to be read in connection with the accompanying drawings, in which:

. Fig. 1 is a block diagram of a high Q LC circuit and Figs. 2, 3, 4 and 5 are graphical illustrations, the ve figures being useful for explaining the theory of the edger pulse and its utility in the generation of waves and pulses according to the principles of my invention;

Fig. 6 is a block diagram of a system for producing damped waves and pulses;

Fig. 7 is a schematic wiring diagram of part of the system of Fig. 6;

Fig. 8 is a schematic wiring diagram of a modified form of edger pulse generator; and

Fig. 9 is a graphical illustration of input and output pulse shapes for one operation of the generator shown in Fig. 8.

Before describing the system in which I employ the edger pulse for producing waves and pulses of selectable frequency and width respectively, it is believed desirable to first discuss the theory leading up to the edger pulse, its generation and use in my invention. It is known that a voltage Wave of a particular frequency may be generated by shock exciting', by means of a current pulse, a resonant circuitwsuch as indicated in block diagram at I0, Fig. 1, tuned to the desired frequency. A rectangular current pulse such as indicated at `I2 in Fig. 2 having a Width is usually employed for a desired frequency the period of which is equal to t. The oscillations produced in the circuit I0 in response to the pulse I2 are illustrated by the curve I4. The leading edge Ylli of the pulse I2 shock excites the circuit into oscillation producing a positive voltage undulation I1 during the first half of period t and tends normally to produce, in the second half of the period t, a negative undulation I8, and so forth as indicated by the broken lines. The trailing edge I9 of the pulse I2 operates to shock excite the circuit in a negative direction producing undulation 20 which combines with the undulation I8 to produce the ultimate undulation 2l from which the circuit continues to oscillate as indicated by the curve I 4.

When the LC circuit is tuned to a period which is twice the width of the exciting pulse, an oscillation will be produced having maximum amplitude characteristics. This is indicated by the curve 25 of Fig. 3 in which f1 indicates the tuned frequency the period of which is twice the width ters the force of the oscillation set up in the cirv cuit by the leading edge thereby substantially cancelling each other. This opposite oscillation effect is indicated by the broken lines 21-a nd 26. If the circuit has a high fQ the-.two opposed oscillatory energies will be Substantially equal increases. Thus, for a given band such as indicated by the limits 45 and 46. the amplitude of the resulting wave is substantially constant for any of the frequencies therebetween. It is this fact that makes the edger pulse of material importance in electrical circuits where a production of waves of substantially a given amplitude characteristic kfor any desired frequency in a given wide band are desired. As Iwill be described hereinafter the edger pulse is also important for the l production of pulses of any desired width within given limits.

In Fig 6, I have illustrated by block diagram up, system for :generating an edger pulse and for and completely cancel each othenout. If the circuit is of a lower Q, the later shock excitation will dominate and produce a small oscillation which, however, may be disregarded in this discussion. V

' This latter tuning yeffect is indicated at fz on the graph of Fig. 3 indicating that .the output wave is of zero amplitude. Forgfrequency adjustments between fr and f2, the variation in amplitude of the ultimate oscillation is indicated .by the curve 25.

' From the foregoing discussion, it is apparent that if the LC circuit Illl were shock excited by a unit pulse 30 (Fig. 4), that is to say `by a pulse one edge of which is substantially vertical and which extends in width from such edge into innity, the circuit would always respond as though it were shock excited by the one edge only. Thus, by using a theoretical unitpulse, or pulses of extremely long duration, Waves of substantially a given amplitude characteristic could be produced by merely varying the tuning of the LC circuit. A plurality of waves of diiferent frequencies that may be obtainable by shock excitation of a high Q LC circuit by a unit pulse are shown at 3|, 32 and 33 of Fig,k 4.

The production of the theoretical unit pulse, however, is not practical but, ,according to my invention, IV produce an edger pulse which approaches the advantages obtainable from the theoretical unit pulse, As hereinbefore described, the edger pulse comprises a substantiallyvertical edge 36 which corresponds to the vertical edge of the unit pulse and an opposite `edge which curves gradually as indicated at 31. The action of the edger pulse on the high fQ LC circuit is indicated by the curve 40. The leading edge 36 shock excites the circuit as indicated by the broken line 4l. circuit simultaneously in the opposite direction as indicated by the broken line Y42.. The curvature of the trailing edge, however, is' such that the shock excitation produced thereby is negligible compared to the shock excitation produced by the vertical leading edge. Thetwo excitations therefore produce a resultant oscillation inthe circuit as indicated by the curve 4l).Y

Fig. 5 shows two curves l38a and 31a of an amplitude-frequency graphV indicating the change of amplitude of the oscillations producible by a theoretical unit pulse and an edger pulse, respectively. For very low frequencies the unit pulse would theoretically produce high amplitude oscillations which, as the frequency is increased, are reduced inversely proportional to the frequency in accordance with the increased power required for the higher frequencies as indicated by the curve Sila, The curve 31a has a lower curvature and tapers 'into the ,curve 30a as the frequency The curved trailing edge 31 shock excites the using itlinthegeneration of waves of desired frequency and for producing pulses of desired widths from ,input wavesregardless of the shape and frequency thereof. The input 50 is applied to a clipper amplifier 52 whereby the Wave form, whether sinusoidal as indicated at 53 or rectangular as indicated at 54,*is gate clipped and amplilied to produce a given rectangular shape as indicated by the rectangular pulse 56. The rectangular pulse 56 is applied tothe edger pulse generator 58 whereby the edger pulse 62 is produced, In order to avoid corner elects in the curve portion 63 of theedger pulse, the generator preferably `includes a diiferentiator -60 for producing an impulse'l corresponding to the leading edgeof the rectangular pulse 56. This positive impulse 6| is used to trigger a pulse producing circuit 64 whereby the edger p ulse 62 is produced. The details of this circuit are shown in Fig. 7 and will be discussed in detail hereinafter. The edger pulse 62 is applied `to a damped wave generator circuit 66 whereby the vertical edge portion of the edger pulse shock excites the generator into oscillations substantially as indicated at 68. The next succeeding edger pulse will produce wave 69, it being understood that the energy of each wave is damped out before the next shock excitation of the circuit.

The wave trains 68 and 69, each of which corresponds to a single excitation by separate edger pulses, maybe Vused for various purposes. The damped waves may, for example, be used for calibrating the tracing on a cathode ray oscilloscope. This may be accomplished by applying thewave directly tothe deecting electrodes of the oscilloscope or the wave may be clipped and diiferentiated. to produce impulses which are applied to the deecting electrodes.

Byconnecting the output circuit 10 through switch 1l to a damper circuit 12,-lt is possible to produce a pulse from each of the damped waves produced by the circuit 66. The damper circuit operates to pass the rst undulation 14 of a Wave and to ydamp .out the remaining portion of the wave` The undulation 1li when applied to a pulse shaper 16 is reshaped to produce a preferred rectangular pulse 18 the Width of which is equal to one half the vperiod of the frequency of wave 68. Thus, Vby merely varying the tuning of the circuit 66 pulses of different widths may be produced.

The circuit of Fig. 7 shows schematically the details of the edger pulse generator 58, the damped wave generator circuit 66 and the damper circuit 12. The diierentiator 60 is the usual condenser-resistor type, except that the resistor thereof isalso used for applying a negative bias on the grid of tube 82. This negative potential biases the tube B2 of the pulse producing circuit 64 to cut-olf so that it is normally non-conductive. The tube circuit includes a condenser 84 connected between the plate and cathode electrodes of the tube. The plate current is supplied through a'resistor 85 so that the condenser 84 is charged exponentially as indicated by the curved portion 630i thev edger pulse 62. When the positive impulse 6| overcomes the cut-olf bias on the tube 82, Ythe tube is caused to conduct and discharge rapidly the charge on the condenser 84. This produces the substantially vertical edge portion of the edger pulse and the subsequent recharging the condenser 84 produces the curved portion The edger pulse is applied through resistance 88 to the damped wave generator circuit 66 which includes a condenser 90 and an inductance 92 either or both of which may be adjustable. The vertical edge of the edger pulse shock excites the tunedcircuit at whichever frequency it is tuned and since the curved edge portion 63 has negligible effect on the circuit, the circuit acts as though it were shock excited into oscillation by a unit pulse. Thus, fora given wide band of frequencies, the oscillations produced by the circuit are of substantially a given amplitude characteristic.

The damper circuit 12 includes a diode having the plate and cathode electrodes 94 and 95 connected across the inductance 92. The undulation 14 produced by the vertical edge portion of the edger pulse being of negative polarity prevents the diode tube from conducting but, as the oscillations pass'through Zero and become positive, the diode conducts thereby sharply reducing the Q of the tuned circuit to absorb the oscillatory energy set up by the vertical portion ofthe edger pulse. Thus, the damper circuit passes the energy of the first undulation 'I4 and damps out all further tendency of the circuit to oscillate. The undulation 14, of course, may be shaped as desired at 18.

In Fig. 8, I have shown a modified form of the edger pulse generator. The circuit generally is substantially the same as shown in Fig. '7 with the exception that the grid of the tube |82 may be biased with zero potential as indicated by the present position of the switch |83 or with a negative bias similarly as in the circuit of Fig. 7. The resistor |80 and the condenser IBI, however, are here chosen of such time constant as not to operate as a differentiator circuit, thereby passing the incoming pulse substantially as received. The plate circuit includes an inductance |86 and resistance 204 which is used for smoothing out corner eects that are produced in the curved portion of the edger pulse when a rectangular pulse is applied to the grid of the tube |82.

Assuming that a negative pulse |90 is applied to the grid of the tube |82, while the tube is at zero bias, the negative pulse drives the tube to cut-01T thereby permitting the plate current to charge the condenser |84 for the duration of the negative pulse thereby producing a curved buildup portion constituting a curved leading edge ISI for the edger pulse. The inductance |86 and resistance 204 operates to smooth out the corner eifect indicated at |93 which would other- Wise be produced by the abruptness of the leading edge of the input pulse. When the trailing edge of the input pulse occurs thereby returning the tube to zero bias, the condenser |84 discharges rapidly thereby producing a substantially Vertical trailing edge |92 for the edger pulse.

It will be seen that by thus operating the circuit of Fig` 8, an edger pulse is produced in which the leading edge is curved and the trailing edge is substantially vertical. By changing the switch 6. |83 to apply a negative potential to the grid of the tube |82 thereby'normally driving the tube to fout-Orhan edger pulse will be produced for positive input pulses wherein the leading edge issubstantially vertical andthe trailing edge is curved. This is illustrated graphically in Fig. 9 wherein positive pulse 200 is applied to the grid of the tube |82 with the tube biased to cut-ol. The leading edge of the input pulse 200 causes the tube |82 to conduct and discharge the condenser |84 thereby producing the substantially Vertical edge 20| for the edger pulse. The tube |82 is caused to flow for the duration of the pulse 200 which, in the absence of the inductance |86, would producea constant Voltage condition as indicated at 202 on the edger pulse. The trailing edgeiof'the input pulse 200 returns the tube to cut-off thereby permitting the condenser |84 to Arecharge as indicated by the curved portion 203. -The inductance |86 and resistance 204, however,

smooths out the corner eiiect produced by the constant current ilow indicated at 202 thereby producing a final curved trailing edge for the edger pulse which is of negligible eiect when applied to the tuned circuit 66 of Fig. 7.

From the foregoing description, it will be readily apparent that by generating an edger pulse I am able to produce, by shock exciting a tunable circuit therewith, waves having a given amplitude characteristic for frequencies covering a wide band, and that by means of av damper circuit and shaper stage, to produce pulses of different widths. It will also be readily apparent that, where the energy of each wave is damped out prior to the occurrence of the next wave, the frequency of the waves is independent of the frequency of the input wave or the repetition of the input pulses or the width of the output pulses.

While I have described above the principles of my invention in connection with speciiic apparatus, and particular modications thereof. it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention and the accompanying claims.

I claim:

1. A system for producing for each input pulse an output pulse of any desired width within given limits comprising means responsive to each input pulse for producing an edger pulse having leading and trailing edges in which one of said edges is substantially vertical and the otherof said edges is curved gradually, a resonant circuit tuned to a frequency the period of which is twice the desired pulse width, means to apply said edger pulse to said resonant circuit, whereby the circuit is shock excited into oscillation by said Vertical edge, the curved edge having negligible effect upon such oscillations regardless of the frequency to which said circuit is tuned and the width of said input pulse, means connected across said resonant circuit to permit one undulation to occur and damp out further tendency of the circuit to oscillate in response to an edger pulse, and means for shaping said one undulation into a pulse of substantially rectangular shape.

2. The system dened in claim 1 wherein the means connected across said resonant circuit includes a diode tube.

3. A system for producing for each input pulse a wave of substantially a given amplitude characteristic for any desired frequency within a given wide band of frequencies comprising means responsive to each input impulseV for producing an edger pulse having leading and trailing edges in which one of said edges is substantially Vertical and the other of said edges is curved so gradually that when said edger pulse is applied to a resonant circuit said other of said edges has substantially negligible effect thereon, a damped resonant circuit tunable to any desired frequency in said band, and means to apply said edger pulse to said resonant circuit to shock-excite said circuit into oscillation at its tuned frequency in response to substantially only said vertical edge.

4. The system defined in claim 3 in combination with means to reshape the input pulse to. insure a substantially rectangular input pulse shape.

.5. The system dened in claim 3 wherein the input pulse is of rectangular shape and the means for producing the edger pulse therefrom includes means for diierentiating said input pulse to pro.- duce a sharp impulse corresponding to one of the leading and trailing edges thereof.

6. The system dened in claim 3 wherein the input pulse is of a rectangularshape and the means for producing the edger pulse therefrom includes an inductance to smooth out any corner effects produced in said other edge due to the rectangular shape oi said input pulse,

'7. A system for producing for each input pulse a Wave of substantially a given amplitude characteristic for any desired frequency Within a given Wide band of frequencies comprising means re` sponsive to each input pulse for producing an edger pulse having a substantially vertical leading edge and a. trailing edge exponentially curved so gradually that when said edger pulse is applied toa resonant circuit said trailing edge has substantially negligible eiect thereon, a damped resonant circuit tunable to any desired frequency in said band, and means to apply said edger pulse to said resonant circuit to shock-excite said circuit into oscillation at its tuned fre,- quency in response to substantially only said leading edge.

8. A system for producing for each input pulse a wave of substantially a given amplitude characteristic for any desired frequency within a given wide band of frequencies comprising means responsive to each input pulse for producing an edger pulse having the leading edge curved to represent a gradual build-*up and the trailing edge substantially vertical, theleading edge be..V

ing curved so gradually that when said edger pulse is applied to a resonant circuit said 1eading edge has substantially negligible effect there on, a damped resonant circuit tunable to any-desired frequency in said band, and means to ap-V ply said edger pulse to said resonant circuit t shock-excite said circuit into oscillation at itS tuned frequency in response to substantially .only said trailing edge.

9. A system for producing damped .waves of substantially a given amplitude characteristic for any desired frequency Within a given wide band of Afrequencies regardless of the frequency or une dulation shape of the input wave energy, Cmm-4 prising means for producing a substantially rec! tangular pu`se for each undulation of said input wave, :means responsiveto each rectangular pulse for producing an ledger pulse in which one of the leading and trailing edges thereof is substam tially vertical and the other is curved S0 `sradually that `when said edger pulse is applied .to a resonantcircuit said other of said edges has lsub-f stantially negligible effect thereon, a `damped resonant circuit tunable to any desired frequency in said band, and means to apply each edger pulse to said resonant circuit toshockseiicite said circuit into oscillation at its tuned frequency in response to substantially only said vertical edge.

1.0. A system for vproducing pulses of any desired width within given limits in response to in, putiwave energy regardless of the frequencytor undulation shape of the input Wave energy comprising means for producing a substantially rec.. taugt/liarv pulse for each undulation of said inmit Wave, means responsive to each rectangular pulse for producing an edger pulse in which one of the leading and trailing edges thereof is substantially vertical andthe other is curved so gradtially that when said edger lpulse is applied to a resonant circuit said other of said edges has-sub- Stantla-lly negligible effect thereon, a damped resonant circuit tunable to any desired frequency in said band, means to apply said edger pulse to Said resonant circuit. to shock-.excite said circuit into oscillation at its tuned frequency in response t0 substantially only said vertical edge, and means connected across said resonant circuit to permit one llndulaion of each damped wave thus produced to pass and to damp out further tendency Gf the circuit to oscillate for such damped wave, and mea-ns for shaping said one undulation into a pulse pf; Substantially rectangular shape.

1l. A system for producing an edger pulse in" response to an input pulse of any wave form comprising ,means to reshape vthe input pulse to insure a Substantially rectangular input pulse Shape, a VdCllllm tube, a condenser, means connecting said condenser between the plate and cathode electrodes of said tube, a resistor, means t0 supply the plate electrode with current through said resistor whereby said condenser is charge.- able exponentially, and means to apply said rectangular input pulse to the grid electrode of said tube to control conduction of said tube for rapid discharging oi Said condenser in time relation with one of the edges of said input pulse to pro-Y duce a substantially vertical edge for Vsaid edger pulse, the-opposite edge of said edger pulse being curved according to the charging characteristics o f said condenser and said resistor.

h l2. 'lhe system dened in claim l1 in combination with means for negatively biasing said tube to cutfoi, and wherein the means for applying the input pulse includes means vfor dilerentiat.- lng the rectangular pulse thereby producing sharp impulses corresponding to the leading and trailing edges of said vinput pulse and means to apply one of said impulses to the grid of said tube to make the yleading edge of said edger pulse substantially vertical and the trailing edge curved exponentially, the vertical edge thereof corre= sponding in time to said one impulse,

13, The system dened in claim 1l in combina.- tion with means for negatively biasing said tube to cut-oil?, and. wherein the means for applying the .input P11156 i5 arranged. t0 apply the 11.113111? pulse with positive polarity to make the leading elle@ 0f Said edger pulse substantially vertical and the trailing edge Curved, and the means for supplying the plate electrode with current includes an inductance which operates to smooth out any corner effects produced in the curved edsee due to lthe rectangular shape of said input pu 1.4. The system defined in claim 11 in combination with means to apply zero bias on said tube, and wherein the means for applying the input pulse is arranged to apply the pulse with negetive polarity to make the leading edge of said edger pulse curved and the trailing .edge substantially vertical, and the means for supplying the plate electrode with current includes an inductance which operates to smooth out any corner effects produced in the curved edge due to the rectangular shape of said input pulse.

15. A system for producing an edger pulse in response to an input pulse of substantially rectangular shape comprising a Vacuum tube, a condenser, means connecting said condenser between the plate and cathode electrodes of said tube, a resistor, means to supply the plate electrode with current through said resistor whereby said condenser is chargeable exponentially, said means including an inductance, and means to apply said rectangular input pulse to the grid electrode of said tube thereby producing current ow through said tube for the duration thereof and thereby causing rapid discharging of said condenser in time relation with one of the edges of said input pulse to produce a substantially vertical edge for said edger pulse, the opposite edge of said pulse being curved according to the charging characteristics of said condenser and said resistor, said inductance operating to smooth out any corner effects produced in the curved edge portion of the edger pulse because of the rectangular shape of the input pulse.

DONALD D. GRIEG.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

